Answer:
21.25 m/s
Step-by-step explanation:
AVERAGE SPEED=
= \frac{s1 t1+ s2t2 + s3t3}{t1 + t2 + t3}=
t1+t2+t3
s1t1+s2t2+s3t3
= \frac{20 \times 10 + 30 \times 5 + 15 \times 5}{10 + 5 + 5}=
10+5+5
20×10+30×5+15×5
= \frac{200 + 150 + 75}{20}=
20
200+150+75
= \frac{425}{20}=
20
425
= 21.25 ms=21.25ms